The present invention relates to an improvement of a reference scatterer for use in the correction of scattering photometers.
In the analysis of samples, there are utilized a variety of detection principles, of which the scattering photometric method is widely used for analyzing liquid samples as well as the absorbance photometric method. The scattering photometric method is able to detect the turbidity of liquid samples with high sensitivity, whereby various objectives of the analysis come to be achieved with the improvement of apparatus for measuring the luminous intensity of scattered light. This enables analysis with great accuracy such as, for example, the analysis of a microquantity of immune albumine contained in blood through the utilization of the antigen-antibody reaction in the clinical examination, and the analysis of the molecular weight of a macro-molecule.
Nevertheless, in order to obtain the high accuracy of quantitative determination at the time of such analysis as above-mentioned, the provision of a superior kind of correcting means is required over and above the sensitivity of the instrument. In the case of the absorbance photometric method, the appropriate correction of the instrument can be made by running a sample blank and then checking the blank value against the 100%-indication of the meter. But such a procedure by a blank test is not useful for the scattering photometric method, as easily understood from its measuring principle. There is no choice in this case but either to adopt another standard for scatterers in place of the sample blank test or to conduct some analytical procedure on both an unknown sample and a sample of already-known concentration with the object of finding the analytical value of the unknown sample through the correlation between the above-mentioned two.
However, the latter procedures require a large quantity of analytical grade reagent. Accordingly, it is not only uneconomical but also at the same time it takes much time and labor because standard samples must be made each time when treating the samples resulting from the reaction, for example, such as the antigen-antibody reaction whose turbidity is liable to fluctuate with time. And what is worse, there is no guarantee of being able to obtain at all times a standard sample for the substance to be analyzed. There are frequent occasions when it is extremely difficult to procure the standard sample according to this method.
To overcome the problem in such a case, it is important to standarize the analytical process as well as the correcting means. Among others, as the standard for correcting the scattering photometer which is employed in measuring the quantity of scattered substances dispersed in solution, heretofore in general there has been used a liquid-phase reference scatterer which had aluminum oxide powder, polystyrene latex or the like dispersed in solution. However, a liquid-phase reference scatterer of this type is insufficient to correct a scattering photometer of high accuracy because its scattered particles are liable to aggregate and bond together within the solution, so that the homogeneous dispersion of particles can not be maintained for a long period of time.
Under these circumstances, there has been developed previously a reference glass scatterer. In this reference glass scatterer a small quantity of foreign matter was added to silicon oxide as the main ingredient of glass, and after both were fused together, they were annealed at proper temperature to make microcrystals as a phase splitting of borosilicic acid grown with the foreign matter as nuclei (Japanese Patent Disclosure No. 20914-1976). The grain diameter of the microcrystal depends on the temperature and time of annealing. If these conditions are fixed and observed, it becomes possible to obtain a reference glass scatterer having the desired particle size distribution. Unlike the before-described liquid-phase reference scatterer, the reference glass scatterer thus constructed had excellent the long-term stability and reproducibility and has been used so far for the correction of scattering photometers of high accuracy.
Nevertheless, the reference glass scatterer main body 1 has an uneven, or rough though fine surface. This is shown in a partially enlarged view in FIG. 1 as a result dirt and moisture easily adhere to the surface, while, on the other hand, it is hard to remove them therefrom. There is further the fear of the surface being injured in trying to wipe the dirt and moisture off while cleaning. The phenomenon of such uneveness arises from the fact that since the particles of the microcrystals 2 are harder than the glass portion 3, the latter is more readily to be cut away in the process of grinding the surface. FIG. 2 is a partially enlarged view of the surface of an ordinary glass body enlarged in the same way as in FIG. 1.
In the case where a reference glass scatterer having a flaw or dirt on its surface is used a series of phenomena occur such as the absorption, reflection or refraction of light, as a sequel to which the reference value acquired can be often wrong. On the other hand, glass is apt to absorb moisture which remains on the surface of the reference glass scatterer and has the same influence as the above-mentioned dirt. There are other points in question, for example, such as the unevenness of the surface of the glass scatterer fluctuates depending on how the grinding operation has been done. Because of this the scattering power of the thus-manufactured scattering plates are likely to vary widely.